


Slippery Passages

by Jinngersnap



Category: Gravity Falls
Genre: Gross, M/M, PWP, Rimjobs, Rimming, Smut, Weird Demon Anatomy
Language: English
Status: Completed
Published: 2015-01-12
Updated: 2015-01-12
Packaged: 2018-03-07 06:36:36
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,862
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/3164945
Author URL: https://archiveofourown.org/users/Jinngersnap/pseuds/Jinngersnap
Summary: <blockquote class="userstuff">
              <p>((repost to new account!!))<br/>Dipper makes a mistake in questioning Bill’s skill with his tongue (and how long it can get…)</p>
            </blockquote>





	Slippery Passages

**Author's Note:**

> (still laughing at the fic title oh my god)
> 
> This is gross I am so gross   
> this is the grossest thing and I am so happy, i am smiling so fucking wide,   
> this started out as a “haha what if Bill has a long tongue and puts it //THERE// and Dipper is like ‘WHAT’   
> what if...”
> 
> and now here we are, this fic belongs in the fucking trash

Horror movies weren't that big of a deal once you had to deal with real monsters in the flesh.

And watching a movie about a human devouring demon while sitting close to a real one seemed like the pure definition of a red herring.

Dipper was getting to the point where these types of things didn’t affect him at all. Swamp monsters seemed clumsy, vampires were becoming gaudy and overdone, and even watching someone transform into a werewolf was nothing like seeing it happen in real life. Scary movies were mostly silly now - or slightly exciting, knowing that he had seen such things with his own eyes, and - most of the time - he has outsmarted them. If anyone should be making a movie about monsters, it should have been him.

Preferably starring him as well. Or at least an actor with dashing good looks.

Bill, on the other hand, liked them. Then again, he liked most things that played on the television, despite what genre it was. He claimed to like all the human endeavors at TV entertainment, or enjoyed seeing them suffer at the hands of horrible acting and bad effects. The only things he seemed to truly enjoy were really bad comedies (something Dipper would classify as ‘very dry humor’), or things on the discovery channels. The demon had actually taken a (very surprising…) liking to a show about meerkats, but that was a different story entirely.

It wasn’t the first time Bill had stayed over at the shack for a horror movie. Luckily Mabel was gone for the night, and she didn’t have to witness Bill and his ‘sitting close together because that’s what humans do during scary movies’ trope. Luckily, the man was lanky, which meant sharing the yellow chair in the Shack’s living room wasn’t that hard at all, and it wasn’t as if Dipper wasn’t getting used to Bill wanting to be… ‘close’.

_Close_  just normally meant things that were… privately shared locked away and containing things that he would never,  _ever_ tell to another living person. It took him long enough to explain to Bill the difference between acceptable PDA and…  _not acceptable_  PDA.

Which Bill still didn’t follow all the time…

But Dipper wasn’t focused on the random public encounters with the demon - right now, things were calm. The movie was… horrible, cliché in every sense that a demon movie  _could_  be. Overzealous possessions, heads spinning, horrible acting and makeup that Mabel could do better while sleeping. It was fun, nonetheless. Mostly since Bill was very skeptical of the events playing out on the screen, constantly bringing up how ‘ _that isn’t how demon possession works - you know that firsthand!’_  and _‘there’s no way holy water even works, it doesn’t even mildly sting’_  or, Dipper’s personal favorite, _‘why are these two humans kissing now, what purpose does this serve to the story?’_.

Currently, he was scoffing over the ‘demon’ in the story trying to appear dangerous and scary by giving a long growl, tongue shooting out and easily reaching down well beyond his neckline. The human ‘victim’ in the movie gave a disgusted scream, but Bill was only holding out his hand to gesture at the screen.

“Unlikely. Also a huge hassle.”

“Why is it a hassle, Bill?” Dipper’s tone was mildly monotone, a hint of amusement hidden underneath. It was how this normally went - Bill would complain, Dipper would ask why, and then Bill would explain.

“This isn’t even a shapeshifting demon, the odds of them having the ability to grow a tongue like that is unlikely.”

“They could just have it inside their mouth, Bill.”

The man scoffed a bit, “No. Wouldn’t be able to talk then. Look how long that is,” the screen showed the demon in question threatening to run the tip of its tongue across the woman’s cheek. “This is poor planning.”

Dipper gave a laugh, “You are talking from experience?”

Bill looked to him with a very matter-of-fact expression, “Yes. I can I can do a  _lot_  of things with this body, Pinetree. You know this.  _From experience_.”

Dipper’s mouth closed into a straight line - it was a bad idea to ask Bill a question like that. Then again, it was always hard to tell where the demon was going to take things… Conversations turned into things like this at the flip of a coin.

“Besides,” Bill turned his attention back to the small television. “Why use a tongue like that for scaring some broad. There are so many other things you can use it for. At least, from a human’s point of view, I’d expect this to go somewhere else.”

He talked with a cocky tone, making Dipper turn his head and open his mouth to ask exactly what Bill meant - to ask what Bill even wanted to  _use_  that tongue for. But the second the thought came to his mind, he was smart enough to close his mouth once more. No - he wouldn’t make that mistake twice in a row. He wasn’t going to ask Bill questions that got him into weird predicaments. Again.

He turned his attention right back at the television, but he could see Bill smirking out of the corner of his eyes. When Bill began to lean closer, Dipper pretended not to notice at all, trying to focus on the woman now trying to run away from a demon - something he empathized very dearly in that moment. But Bill was leaning close, and he felt the warm breath on his neck that he  _couldn’t_  so easily ignore.

“Your thoughts are always very tasty, Pinetree,” Bill purred out, voice low and… God, Dipper hated to admit it, but sounding alluring… smooth and inviting. Very inviting.

This wasn’t going to end well.

“It’s—… It’s still rude of you to even read my mind, Bill.”

He felt lips against his neck. Not kissing ones. Smirking ones, grinning right against his skin. “It’s rude of you to have such loud thoughts.”

Dipper knew there was no point in picking a fight, so instead he gave a small gulp, neck beginning to tilt as he felt a wet tongue slide across it. A… normal tongue, right? Nothing weird, nothing creepy, just Bill attempting foreplay again. A bit of tongue definitely wasn’t weird at all.

Until he felt the tongue slide down his neck, and a hand wrap around him and hold the other side of his head, keeping him in place as the wetness traveled. “W-Whoa, okay now…!”  _That_  was weird. And his reaction got Bill to snicker, body moving closer as his other hand wrapped around the boy to bring him almost into his lap. Dipper wasn’t fully sure if what he was feeling was actually real - Maybe Bill was just trying to trick him up. But the second he felt the wet tongue easily reach his collarbone, despite Bill still breathing near his ear, he knew he had to be right. His hands gripped at his knees, jeans twisting slightly under fingers as he tried not to make  _noises_  about this. Good noises? Bad ones? He wasn’t sure, but he knew he’d be embarrassed by them nonetheless.

Bill pulled away then, tongue returning to his mouth and seeming to go back to a ‘normal’ size. He was laughing, grinning wide as he tugged on Dipper’s body and brought him to fully sit in his lap. “You really are easy, Pinetree. All of your blood is in your cheeks now.” He brought his teeth to Dipper’s ear, giving the shell a small bite, “You’re blushing here, too.”

It got Dipper to hunch a shoulder, head tilting into the bite in an attempt to get him to stop. “You’re…! Being  _weird”_ he huffed it out, not exactly fighting as Bill pulled his back to lie against his front - ignoring the fact that he was essentially straddling the demon backwards.  What he hated most about this was that his body was already finding it exciting - something he hoped Bill wouldn’t catch onto very quickly… Even though he  _always_  did.

“Weird,” Bill repeated the word, tongue now running across the back of Dipper’s neck and getting the boy to give a nervous chuckle. “Yet you’re not struggling. You could get up, if you wanted. Couldn’t you?”

Once again, Dipper felt a smirk across his skin. Bill was right… Dipper had rejected the Demon a lot in the past, simply pushing him off or giving a firm ‘No’ or ‘Not right now’ when the time wasn’t right, or Bill was just being a huge asshole.

Even so, he wasn’t moving. He could, sure, but the tongue across his skin and the hands lying on his waist were distracting, the horror movie doing… no help in getting his mind off things. At all.

When he showed no real struggle, Bill grinned and continued, hands running down his legs and then up again, taking Dipper’s jacket and getting him to shrug out of it. With the coat now draped across the arm of the recliner, hands ran beneath Dipper’s shirt, getting his stomach to clench from the warm touch. No gloves - for once. Bill was rather ‘domestic’ looking this night, a simple dress shirt in place of a full suit and warm gloveless hands pressing against skin, traveling up…

Dipper hated that he gave noises so easily, especially at something as simple as nipples being pinched, twisted slowly. Added to the sensation of the tongue again, and he was already closing his eyes, not focused on the movie anymore and trying not to arch his hips forward. That’d give him away completely, after all.

The tongue was traveling, down the back of his neck and twisting around to run against his collarbone. It was… strong, enough to make Dipper tilt his head, another nervous laugh leaving him as the wet organ pressed against his adam’s apple. Weird, but not exactly the weirdest thing the demon had done. He could… deal with this.

He felt as a hand left from under his shirt, soon coming to press on his jawline and twist his head, tongue now running along his lips. It felt… normal sized now (He wasn’t going to even attempt to understand Bill’s shapeshiting abilities, best to just… accept it and move one, at this point). Without even being persuaded, Dipper’s lips opened, allowing the demon to fully kiss him, tongues (normal sized, thank god…!) pressing against each other in an already heated manner. Dipper did have to admit one thing - as clumsy as Bill started at all this… romantic intimate stuff, he had  _definitely_  gotten pretty damn good at it. The rough and wet kisses were always good, good enough to get him to groan slightly into Bill’s mouth as his upper torso twisted, shoulder against Bill’s chest as he attempted to actually kiss back. For once, Bill seemed to be going slow.

That is, until Bill’s free hand pressed down on Dipper’s groin, making the boy gasp and groan into the kiss, fully aware now at how much some simple licking had affected him. The moaning only got Bill to smirk, and the kiss took over his mouth once more, this time more overpowering, pressing against his body, his mouth suddenly…! Feeling  _very_  full…!

Dipper’s hands went to Bill’s shoulders, pressing hard and getting the demon to get  _out_  of his mouth. For the first time that night, he saw the tongue slowly slide back into Bill’s mouth, back behind grinning teeth, and Dipper quickly wiped his mouth off with his arm. “Don’t…! Don’t do that in my _mouth!”_

Bill still grinned, pressing lips to Dipper’s jawline as he spoke, “Why not, Pinetree? You were enjoying it so far.”

“N-not…! Not in my mouth, I don’t want that thing down my throat, you could have…! Choked me, or something, j-jeeze.”

“So you want me to do  _other_  things with this tongue.”

“No,” Dipper tried to shrug off Bill’s lips, “You totally killed the mood.”

“Oh,” Bill was grinning against his skin again, the hand near his groin pressing down again, grabbing tightly onto the tenting that was there, getting Dipper to let out a sudden whine. “I think the mood is still fine, kid. In fact, you gave me an idea.”

Dipper tried to shake his head - there was no way he was going to agree to this. Not here. “Not… Jesus, Bill, can we at least… I don’t,  _don’t,_ want to do this out here, not in this… chair.”

Bill gave a groan, “More of this ‘ _I can’t do anything in my uncle’s chair’_ stuff. Humans and their morals. It’s not like he will ever find out.”

Giving a dark glare, Dipper shook his head once. “No. Not here.”

Bill’s body slumped with a small sigh, “Someday, Pinetree. In the meantime…” He looked around, once towards the hallway that led to the stairs, but then grinned, hands wrapping around Dipper’s waist and suddenly moving forward. “How about here, then?”

Dipper fell forward - mostly, a hand still wrapped around him preventing his face from hitting the floor. Instead, his hands and knees quickly met the carpet, and Bill was quick to press his body against his, soon forcing the boy to press his weight onto elbows as he was pushed closer to the ground.

“W—What the  _hell_ , Bill?”

“This isn’t the chair.”

“No, but…!! It’s still in the  _living room_ , Bill!”

“And no one is home, it’s fine.” His body pressed more into Dipper’s, tongue once again running across his neck and traveling up to tickle the shell of his ear.

It got Dipper’s breath to hitch, fingers digging into the plush carpet beneath him. This… wasn’t exactly a good position, and it was one that, once in it, his body automatically became… very aware. Very aroused. Something that annoyed him to no end, mostly because Bill  _knew_  how submissive this was.

It started again, the barrage of touching and licking, Dipper’s shirt being hiked up and nipples once again teased. Nothing close enough to bring him to the edge, but enough to get a small whine out of him. And that tongue… He hated to admit it, really hated it, but it was somehow really… attractive. Sexy. Strong and wet, pressing against his jawline, neck, ears… And soon moving down to run across his spine, something that made him press his chest into the floor while his hips (embarrassingly enough) pressed into the man behind him.

He could tell all of it was making Bill grin. Bill didn’t even have to make any noise, and Dipper could almost  _feel_  when he was grinning. He barely even realized Bill had undone his jeans until they were being pulled down, boxers quickly following and making the position suddenly ten times more embarrassing. But Bill didn’t waste time in teasing him, hand slipping between his legs and cupping his length, rubbing and getting Dipper to groan and press his cheek into the carpet.

His mind didn’t know what to focus on - that tongue swirling against the small of his back, or the hand very softly rubbing at him, making him give soft hums and completely forget the implications of doing this in the living room.

His fogging mind quickly came back to its senses as soon as he felt Bill’s tongue travel somewhere _else_ , pressing between him and suddenly causing his hips to arch in the opposite direction. “-Whoa, whoa, okay…! H-hah,  _that’s_  different…!” He gave a loud gulp, twisting his body to look behind him, catching the dark eyes and grin.

“You seem nervous, Pinetree.” Bill’s eyes stayed on Dipper’s as he moved down, giving a single lick across his behind.

The act got Dipper to feel his face heat up, and he wanted to throw his hand back and hit Bill away, tell him that there was  _no_  way he was about to do what Dipper  _thought_  he was about to do. Before he could, he felt teeth graze his skin, and it got him to turn back around, not wanting to give Bill the face that showed he  _liked_  that… There was  _no way_  he’d give any reason for the demon to add ass-bites onto the list of fun-marks-to-give-pine-tree.

Of course, such a thought seemed redundant as he felt the laugh against his skin, both hands now taking either side of his hips (sadly losing the nice gentle pumps to his length), more bites scattering against the flesh there. It got him to whimper slightly, never much realizing how sensitive the skin there really was. Sure, Bill had his fun every now and then, trying to throw a smack or two (or many…) against his behind when the ‘mood seemed right’. But this was so much more… close. Very slow, a lot more personal…

The tongue came back, then, getting Dipper to not just whimper but let out a shaky noise. He knew where Bill was going to put that tongue, and… While it was something he had  _seen_  before (he had gotten a lot better at cleaning his internet history), and even though he knew this was something that couples ( _hah,_  couples!) did sometimes…

“—Oh god-…” It felt like it came out of nowhere, and it didn’t even press  _into_  him, but feeling the wet organ just slide against him… His arms moved to cover his face, knowing he was blushing wildly, knowing that he was about to make a lot of embarrassing noises….

A few more times, enough to get his hips to squirm. He hated that he  _wanted_  it, even though he knew how gross this was. Leave it to a demon to find nothing gross about this at all… Bill probably didn’t understand why this  _was_  gross! And there was no point in explaining it to him - he wouldn’t hold any regards over what a simple human found disgusting or nasty.

A low, gulping groan left him when he actually felt the tongue press against him, slip inside… Things were already wet, slick from… obvious reasons, so he didn’t need to worry about that… No, instead his mind focused on the feel of it, as much as he didn’t want to. Not a lot of texture, no, smooth… Warm, sure. Wet…

It started off thin, small, and Dipper quickly realized what Bill was really trying to do here. He felt _stupid_  for not realizing it at first, but he felt the organ move  _deeper_ , gradually getting wider, not exactly sure how deep it was moving but knowing,  _knowing…_ And when Bill’s breath hit his skin, the demon’s hands grasping the sides of his behind, spreading…!

Dippers hands were in his hair now, trying to hide so far into his arms that he could maybe disappear, even if his mouth was betraying him with soft moans and his hips were practically shaking at the feeling. He didn’t want to admit it was hot - because it was gross. It was really gross, but he was enjoying it. Maybe it was the taboo feeling of it all, knowing that it was totally wrong but still melting into the feeling inside him.

And then he felt it  _move_. Actually wiggling inside him, reminding him of some sort of tentacle, twisting and writhing. Slowly at first, barely at all, but it grew, making Dipper’s hips roll and arch. Bill was quick to sink nails into his skin, rearranging himself to lift Dipper’s hips higher, the tongue only pressing deeper. Dipper tried to grab at the floor, knees being lifted off the ground as fingers dug into the carpet as if it’d tether him to the ground.

The twisting only got worse, then, each time it did it made sure to press against the small bundle of nerves that made his legs shake. He tried to hide his face again, shaking his head but still moaning with each breath outward. Even without his dick being touched, he felt like he was close to coming, only made worse when Bill would occasionally chuckle against his skin, making the base of the tongue practically  _vibrate_.

It changed, though; right when Dipper felt the pooling feeling of pre-orgasm in his stomach, Bill was pressing him back onto the ground. He would have objected, if it wasn’t for Bill’s hand leaving his behind to wrap around his waist, not even hesitating to take his length in a tight grip.

The moan that came from Dipper wasn’t muffled or small then - calling out and already seeing white. Bill didn’t even have to give more than a few pumps, and Dipper was already pressing his hips forward, clutching at the carpet once more as he emptied quickly onto the floor. He choked out a groan, the clenching and spasms of his muscles making the item inside him seem so much more  _real_ , and Bill waited until Dipper’s body calmed entirely before slipping it out - a strange sensation that got Dipper’s lower half to twitch. Everything seemed suddenly calm then, tiny aftershocks rocking his body but Bill was actually… quiet

He wasn’t sure what the Demon was doing then - quiet behind him, almost waiting for Dipper to catch his breath. Which was a little weird, but Dipper was thankful for it, seriously needing a second to come down from… that, and actually process what happened.

When he began to sit up on his elbows, Bill must have taken it as a sign to grab hold of him, quickly swinging him upwards to sit in his lap. Dipper could  _feel_  that Bill was… still excited about that show that just happened, feeling that said excitement press against his inner thigh without any shame.

But Bill didn’t mention it, pressing his smirk against Dipper’s neck. “You made a mess. In the  _living room,_  of all places.”

Dippers stomach flipped a little at the thought, but luckily a carpet wasn’t too hard to clean. “Shut up,” he sighed out, exhausted but accepting the sort-of-kisses against his skin anyway. Bill never really _kissed_  his skin. He nibbled, licked, and smirked against it. Those  _were_  kisses, to the demon.

And he led those kisses across Dipper’s neck, up to his jawline - something that was calming for the moment, actually sweet.

Until Bill dragged him into a kiss, full and searching, with  _that_  tongue back against his. Once again, Dipper was in a panic mode, switching between the notions of telling Bill to knock it off, and knowing he wouldn’t even understand why this was totally disgusting. But Bill was still in a mood here - he wouldn’t have cared anyway, not the way his hands were still exploring Dipper’s body, totally ignoring the fact that he was soft now - that could, after all, change pretty quickly.

Eventually, Dipper had the strength to push Bill away, getting a snicker from the man. “Gross…” Dipper mumbled out, wiping his mouth yet again. It only got Bill to grin wider, pressing his forehead against Dipper’s while he worked to spin the boy to straddle him properly. His lips were close, but Dipper was having no more kissing right now.

“So, Pinetree,” he hummed out, eye growing narrow as he stared down at him. “About paying me back…”


End file.
